Ultra high resolution liquid crystal display having a compensating thin film transistor at each pixel

ABSTRACT

The present disclosure relates to an ultra high-resolution liquid crystal display having a compensating thin film transistor at each pixel. The present disclosure suggests a thin film transistor substrate comprising: gate lines running in horizontal direction and data lines running in vertical direction which define a plurality of pixel area on a substrate; a first gate electrode and a second gate electrode formed by dividing any one gate line disposed at any one of an upper side and a lower side; a first thin film transistor connected to the first gate electrode; and a second thin film transistor connected to the first thin film transistor and the second gate electrode. The flat panel display according to the present disclosure has an ultra high-density resolution over 300PPI with the high aperture ratio.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Republic of Korea Patent ApplicationNo. 10-2012-0158351 filed on Dec. 31, 2012, which is incorporated byreference herein in its entirety.

1. Field of the Disclosure

The present disclosure relates to an ultra high-resolution liquidcrystal display (or ‘LCD’) having a compensating thin film transistor(or ‘TFT’) at each pixel. Especially, the present disclosure relates toa pixel structure having high aperture ratio for ultra high resolutionLCD having a compensation TFT to compensate the On/Off currentcharacteristics of the TFT for driving the pixel.

2. Discussion of the Related Art

Nowadays, as the information society is developed, the requirements ofdisplays for representing information are increasing. Accordingly, thevarious flat panel displays (or ‘FPD’) are developed for overcoming manydrawbacks of the cathode ray tube (or ‘CRT’) such as heavy weight andbulk volume. The flat panel display devices include the liquid crystaldisplay device (or ‘LCD’), the field emission display (or ‘FED’), theplasma display panel (or ‘PDP’), the organic light emitting displaydevice (or ‘OLED’) and the electrophoresis display device (or ‘ED’).

The display panel of a flat panel display may include a thin filmtransistor substrate having a thin film transistor allocated in eachpixel area arrayed in a matrix manner. For example, the liquid crystaldisplay device represents video data by controlling the lighttransitivity of the liquid crystal layer using the electric fields.According to the direction of the electric field, the LCD can beclassified in the two major types; one is vertical electric field typeand the other is the horizontal electric field type.

For the vertical electric field type LCD, a common electrode formed onan upper substrate and a pixel electrode formed on a lower substrate arefacing with each other for forming an electric field of which directionis perpendicular to the substrate face. A twisted nematic (TN) liquidcrystal layer disposed between the upper substrate and the lowersubstrate is driven by the vertical electric field. The verticalelectric field type LCD has merit of higher aperture ratio, while it hasdemerit of narrower view angle about 90 degree.

For the horizontal electric field type LCD, a common electrode and apixel electrode are formed on the same substrate in parallel. A liquidcrystal layer disposed between an upper substrate and a lower substrateis driven in In-Plane-Switching (or ‘IPS’) mode by an electric fieldparallel to the substrate face. The horizontal electric field type LCDhas a merit of wider view angle over 160 degrees and faster responsespeed than the vertical electric field type LCD. However, the horizontalelectric field type LCD may have demerits such as low aperture ratio andtransitivity ratio of the back light.

In the IPS mode LCD, for example, in order to form the in-plane electricfield, the gap between the common electrode and the pixel electrode maybe larger than the gap between the upper substrate and the lowersubstrate, and in order to get enough strength of the electric field,the common electrode and the pixel electrode may have a strip patternhaving certain width. Between the pixel electrode and the commonelectrode of the IPS mode LCD, the electric field horizontal with thesubstrate is formed. However, just over the pixel electrode and thecommon electrode, there is no electric field. That is, the liquidcrystal molecules disposed just over the pixel electrodes and the commonelectrodes are not driven but maintain the initial conditions (theinitial alignment direction). As the liquid crystal molecules in theinitial condition cannot control the light transitivity properly, theaperture ratio and the luminescence may be degraded.

For resolving these demerits of the IPS mode LCD, the fringe fieldswitching (or ‘FFS’) type LCD driven by the fringe electric field hasbeen proposed. The FFS type LCD comprises the common electrode and thepixel electrode with the insulating layer there-between, and the gapbetween the pixel electrode and the common electrode is set narrowerthan the gap between the upper substrate and the lower substrate. Sothat, a fringe electric field having a parabola shape is formed in thespace between the common electrode and the pixel electrode as well overthese electrodes. Therefore, most of all liquid crystal moleculesdisposed between the upper substrate and the lower substrate can bedriven by this fringe field. As a result, it is possible to enhance theaperture ratio and the front luminescence.

FIG. 1 is a plane view illustrating a thin film transistor substratehaving an oxide semiconductor layer included in a fringe field typeliquid crystal display according to the related art. FIG. 2 is across-sectional view illustrating the structure of the thin filmtransistor substrate of FIG. 1 by cutting along the line I-I′ accordingto the related art.

The thin film transistor substrate shown in FIGS. 1 and 2 comprises agate line GL and a data line DL crossing each other with a gateinsulating layer GI therebetween on a lower substrate SUB, and a thinfilm transistor T formed at each crossing portion. By the crossingstructure of the gate line GL and the data line DL, a pixel area isdefined. In the pixel area, a pixel electrode PXL and a common electrodeCOM facing each other with a second passivation layer PAS2 therebetweenare disposed for forming the fringe field. For example, the pixelelectrode PXL has a rectangular shape corresponding to the shape of thepixel area, and the common electrode COM has a plurality of stripsdisposed in parallel each other.

The common electrode COM is connected to a common line CL disposed inparallel with the gate line. GL. A reference voltage (or ‘commonvoltage’) is supplied to the common electrode COM through the commonline CL.

The thin film transistor T charges and maintains the pixel signalvoltage to the pixel electrode PXL by responding to the gate signal ofthe gate line GL. To do so, the thin film transistor T comprises a gateelectrode G branched from the gate line GL, a source electrode Sbranched from the data line DL, a drain electrode D facing the sourceelectrode S and connecting to the pixel electrode PXL, and asemiconductor layer SE overlapping with the gate electrode G having thegate insulating layer GI therebetween for forming a channel between thesource electrode S and the drain electrode D.

The semiconductor layer SE is made of poly silicon material, as it hashigh electron mobility characteristics. The middle portions of the polysilicon layer SE overlapping with the gate electrode G may be defined asan active layer A (the channel area). The other portions of the polysilicon layer SE except the active layer A may be two conductive areasby plasma treatment. The one side of the conductive area may becontacted with the source electrode S via a source contact hole SH, andthe other side of the conductive area may be contacted with the drainelectrode D via a drain contact hole DH. In other words, the polysilicon semiconductor layer SE comprises a source area SA contacting thesource electrode S, a drain area DA contacting the drain electrode D,and an active (or ‘channel/) layer A overlapping with the gate electrodeG between the source area SA and the drain area DA.

In the fringe field type LCD, the pixel electrode PXL and the commonelectrode COM are overlapped each other. Within the overlapped space, astorage capacitance is formed. In order to form the fringe field and tocharge the storage capacitance enough, the TFT should have highperformance. For example, to satisfy the requirement of the fringe fieldtype LCD, it is preferable to use the thin film transistor substratehaving the poly-silicon semiconductor layer with the top gate structure.

Referring to FIG. 2, we will explain about the structure of the thinfilm transistor having the poly silicon semiconductor material in thetop gate structure. At first, on the substrate SUB a semiconductor layerSE is formed. A gate insulating layer GI is deposited over the substrateSUB having the semiconductor layer SE. On the gate insulating layer GI,a gate electrode G is formed to overlap with an active layer A, which isthe middle portion of the semiconductor layer SE.

On the gate electrode G, an intermediate insulating layer IN isdeposited to cover all surface of the substrate SUB. By penetrating theintermediate insulating layer IN and the gate insulating layer GI, asource contact hole SH and a drain contact hole DH exposing the sourcearea SA and the drain area DA of the semiconductor layer SE,respectively, are formed. On the intermediate insulating layer IN, asource electrode S contacting the source area SA via the source contacthole SH and a drain electrode D contacting the drain area DA via thedrain contact hole DH are formed.

A first passivation layer PAS1 is deposited over the whole surface ofthe substrate SUB having the top gate type tin film transistor T.Further, a pixel contact hole PH exposing some portions of the drainelectrode D is formed by penetrating the first passivation layer PAS1.

The pixel electrode PXL formed on the first passivation layer PAS1 iscontacted to the drain electrode D via the pixel contact hole PH. On theother hand, the common electrode COM is formed to overlap with the pixelelectrode PXL on the second passivation layer PAS2 covering the pixelelectrode PXL. Between the pixel electrode PXL and the common electrodeCOM, the fringe electric field is formed. In addition, within the spaceformed by the overlapping structure of the pixel electrode PXL and thecommon electrode COM, the storage capacitance is formed. By this fringeelectric field, the liquid crystal molecules arrayed in plane directionbetween the thin film transistor substrate and the color filtersubstrate may be rotated according to the dielectric anisotropy of theliquid crystal molecules. According to the rotation degree of the liquidcrystal molecules, the light transmittance ratio of the pixel area maybe changed so as to represent desired gray scale.

The Off-Current characteristics of the thin film transistor having thepoly-silicon semiconductor material may be easily degraded. In order tocompensate this degraded Off-Current characteristics of the driving thinfilm transistor, a compensating thin film transistor may be furtherrequired. Like this case, by adding the compensating TFT in the pixelarea, the aperture ratio may be reduced because the non-transitive areais increased. Therefore, required is a pixel structure in which theaperture ratio is not reduced so much even the compensating TFT isincluded in the pixel area.

SUMMARY

A thin film transistor substrate comprises: gate lines running inhorizontal direction and data lines running in vertical direction whichdefine a plurality of pixel area on a substrate; a first gate electrodeand a second gate electrode formed by dividing any one gate linedisposed at any one of an upper side and a lower side; a first thin filmtransistor connected to the first gate electrode; and a second thin filmtransistor connected to the first thin film transistor and the secondgate electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a plane view illustrating a thin film transistor substratehaving an oxide semiconductor layer included in a fringe field typeliquid crystal display according to the related art.

FIG. 2 is a cross-sectional view illustrating the structure of the thinfilm transistor substrate of FIG. 1 along the line I-I′ according to therelated art.

FIG. 3 is a plane view illustrating the structure of a thin filmtransistor substrate having a compensation thin film transistoraccording to the first embodiment of the present disclosure.

FIG. 4 is a plane view illustrating the structure of a thin filmtransistor substrate having a compensation thin film transistoraccording to the second embodiment of the present disclosure.

FIG. 5 is a cross-sectional view illustrating the thin film transistorsubstrate having a compensation thin film transistor by cutting alongthe line in FIG. 4.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to attached figures, embodiments of the present disclosurewill be described. Like reference numerals designate like elementsthroughout the detailed description. However, the present disclosure isnot restricted by these embodiments but can be applied to variouschanges or modifications without changing the technical spirit. In thefollowing embodiments, the names of the elements are selected for easeof explanation and may be different from actual names.

Referring to FIG. 3, we will explain about the first embodiment of thepresent disclosure. FIG. 3 is a plane view illustrating the structure ofa thin film transistor substrate having a compensation thin filmtransistor according to the first embodiment of the present disclosure.FIG. 3 is the diagram illustrating a thin film transistor substrate foran ultra high definition resolution liquid crystal display over 300PPI,having the compensation thin film transistor in each pixel. Hereinafter,the driving thin film transistor T1 and the compensation thin filmtransistor T2 are named for distinguish each other so it is not requiredthat the order and position of them would be same as shown in thefigures.

The thin film transistor substrate according to the first embodiment ofthe present disclosure comprises a plurality of pixel areas defined by aplurality of gate lines GL and a plurality of data lines DL, which crosseach other with a gate insulating layer GI therebetween. Each pixel areacomprises a pixel electrode PXL and a common electrode COM facing eachother with a second passivation layer PAS2 therebetween, for forming afringe electric field. The pixel electrode PXL has a rectangular shapecorresponding to the shape of the pixel area, and the common electrodeCOM has a plurality of strips disposed in parallel each other.

In each pixel area, one driving thin film transistor T1 is disposed.Further, one compensation thin film transistor T2 is disposed in eachpixel area for compensating the Off-Current characteristics of thedriving thin film transistor T1. The drain electrode D1 of the drivingthin film transistor T1 is connected to the source electrode S2 of thecompensation thin film transistor T2.

Now, we will explain about the structure of the thin film transistorsubstrate having the driving thin film transistor T1 and thecompensation thin film transistor T2 which are connected in serial. Onthe substrate SUB, the pixel areas disposed in a matrix manner aredefined by the crossing structure of the gate lines GL running inhorizontal direction and the data lines DL running in verticaldirection.

The gate electrode G1 of the driving thin film transistor T1 is branchedfrom the gate line GL to the pixel area. The source electrode S1 of thedriving thin film transistor T1 is branched from the date line DL to thepixel area, especially to the gate electrode G1. The semiconductor layerSE of the driving thin film transistor T1 is extended from the sourceelectrode Si and overlapped with the gate electrode G1. The drainelectrode D1 of the driving thin film transistor T1 is not formed as aseparated electrode. The drain electrode D1 would be the drain area DA1.The semiconductor layer SE comprises a source area SA1 contacting thesource electrode S1, a channel area A1 overlapping with the gateelectrode G1, and the drain area DA1 formed at the side opposing thesource area SA1 from the gate electrode G1.

The gate electrode G2 of the compensation thin film transistor T2 is notformed separately. One portion of the gate line DL would be used as thegate electrode G2 of the compensation TFT T2. The source electrode S2 ofthe compensation thin film transistor T2 is not formed separately,neither. The source area SA2 expanded from the drain area DA1 of thesemiconductor layer SE would be the source electrode S2 of thecompensation TFT T2. The drain electrode D2 of the compensation thinfilm transistor T2 is connected to the drain area DA2 formed at the sideopposing the source area SA2 from the gate electrode G2 of thecompensation TFT T2.

In the first embodiment of the present disclosure, in order to connectthe driving TFT T1 and the compensation TFT T2 serially, followingstructure would be preferred as shown in FIG. 3. The gate electrode G1of the driving TFT T1 may be extruded to the next pixel area disposed atthe next row from the current pixel area. The semiconductor layer SE maybe disposed as starting from the next row pixel area, overlapping withthe gate line GL and extending to the current row pixel area. The drainelectrode D2 of the compensation TFT T2 is connected to the pixel areaPXL formed in the current pixel area.

The pixel electrode PXL is overlapped with the common electrode COMhaving a passivation layer therebetween. The common electrode COM isconnected to the common line CL disposed in parallel with the gate lineGL. A reference voltage (or ‘common voltage’) is supplied to the commonelectrode COM through the common line CL. Between the pixel electrodePXL and the common electrode COM, a fringe electric field is formed.Further, within the overlapped space of the pixel electrode PXL and thecommon electrode COM, a storage capacitance is formed. By this fringeelectric field, the liquid crystal molecules arrayed in plane directionbetween the thin film transistor substrate and the color filtersubstrate may be rotated according to the dielectric anisotropy of theliquid crystal molecules. According to the rotation degree of the liquidcrystal molecules, the light transmittance ratio of the pixel area maybe changed so as to represent desired gray scale.

In the case of low density resolution liquid crystal display less than300PPI, the pixel area is relatively large so that the area for thedriving TFT T1 and the compensation TFT T2 is not occupying so muchlarge ratio in the pixel area. Furthermore, in the fringe field type,the aperture ratio can be easily ensured because the storage capacitanceis not formed separately but formed by the overlapping structure of thepixel electrode PXL and the common electrode COM. Therefore, the area ofthe compensation TFT T2 does not severely affect to the reduction of theaperture ratio.

However, in the case of ultra high-density resolution liquid crystaldisplay over 300PPI, the situation is totally different. As the numberof pixel is increasing, the size of each pixel should be gettingsmaller. On the other hands, the size of the thin film transistors T1and T2 should not be getting smaller as the size of the pixel becausethe characteristics of the TFTs should be kept. Consequently, in theultra high-density resolution flat panel display, the area ratio of thethin film transistors T1 and T2 in the pixel area would be gettinglarger. As the area for the TFTs T1 and T2 is the non-transmittancearea, it may be key causes for the reducing of the aperture ratio in theultra high-density resolution.

In the first embodiment, in order to reduce the area ratio of thedriving TFT T1 and the compensation TFT T2 in the pixel area, the gateelectrode G2 of the compensation TFT T2 is not formed separately, butone portion of the gate line GL may be used as the gate electrode G2 ofthe compensation TFT T2. However, it is not enough to ensure theaperture ratio for the case of the super ultra high-density resolutionover 400PPI.

Hereinafter, further referring to FIGS. 4 and 5, we will explain aboutthe second embodiment of the present disclosure. FIG. 4 is a plane viewillustrating the structure of a thin film transistor substrate having acompensation thin film transistor according to the second embodiment ofthe present disclosure. FIG. 5 is a cross-sectional view illustratingthe thin film transistor substrate having a compensation thin filmtransistor by cutting along the line II-II′ in FIG. 4. Here, the drivingthin film transistor T1 and the compensation thin film transistor T2 arenamed for distinguish each other so it is not required that the orderand position of them would be same as shown in the figures.

The second embodiment suggests a super ultra high-density resolution(over 400PPI) liquid crystal display in which the aperture ratioreduction is minimized even if the compensation thin film transistor isfurther comprised. The thin film transistor substrate according to thesecond embodiment comprises a gate electrode, which is not extruded tothe pixel area from the gate line, but one portion of the gate line isused as the gate electrode. Especially, the second embodiment suggestsan example of structure in which the gate line itself is used as thegate electrodes of the driving TFT and the compensation TFT.

On the substrate SUB, a plurality of pixel areas having rectangularshape defined by a plurality of gate lines GL and a plurality of datalines DL, which cross each other. Specifically, one pixel area isdefined by the two data lines DL disposed at left and right sides andthe two gate lines GL disposed at upper and lower sides.

Here, any one of the gate line DL among the upper side gate line and thelower side gate line is divided into two branches for being used as thegate electrode. These two gate electrode formed by the divided gate lineis commonly used as the gate electrode for the current pixel area andthe next row pixel area. That is, one gate line GL may be commonlyallocated to two pixel electrodes which are neighbored in vertical eachother.

Further referring to FIGS. 3 and 4, we will explain in detail. Bydividing the gate line GL in the upper branch and the lower branch, thegate electrode G1 of the driving TFT T1 and the gate electrode G2 of thecompensation TFT T2 are formed. The gate line GL, the gate electrode G1of the driving TFT T1, and the gate electrode G2 of the compensation TFTT2 are disposed in horizontal direction and parallel each other.

As the gate electrodes G1 and G2 are for the upper (or ‘current’) pixelelectrode PXL and the lower (or ‘next row’) pixel electrode PXL, thesemiconductor layer SE may be formed as extending from the upper pixelarea to the lower pixel area and crossing the gate electrodes G1 and G2.

A source electrode S1 of the driving TFT T1 is formed as being branchedfrom the data line DL to the pixel area and being parallel with the gateelectrode G1 of the driving TFT T1. The source electrode S1 of thedriving TFT T1 contacts one side of the semiconductor layer SE.

The semiconductor layer SE comprises a source area SA1 contacting thesource electrode S1 of the driving TFT T1, an active channel layer A1 ofthe driving TFT T1 overlapping with the gate electrode G1 of the drivingTFT T1, a drain area D1 of the driving TFT T1 and a source area S2 ofthe compensation TFT T2, an active channel layer A2 of the compensationTFT T2, and a drain area D2 of the compensation TFT T2.

That is, the driving TFT T1 and the compensation TFT T2 are seriallyconnected each other via the semiconductor layer SE. The semiconductorlayer SE is extended by running from the lower pixel area, passing thegate electrodes G1 and G2, reaching to the upper pixel area. In thatcase, the source electrode S1 of the driving TFT T1 is disposed at thelower pixel area. The drain electrode D2 of the compensation TFT T2 isdisposed at the upper pixel area and connected to the pixel electrodePXL formed at the upper pixel area.

The source electrode Si branched from the left side data line DL issupplied with the data voltage for driving the upper pixel electrodePXL. On the contrarily, the source electrode 51 branched from the rightside data line DL is supplied with the data voltage for driving thelower pixel electrode PXL. The semiconductor layer SE passing the leftside of the gate electrodes G1 and G2 is for driving the upper pixelelectrode. The semiconductor layer SE passing the right side of the gateelectrodes G1 and G2 is for driving the lower pixel electrode. In otherexample, the reversed structure is possible.

The gate electrodes G1 and G2 formed by dividing one gate line GLdisposed at upper side (or ‘lower side’) into two segments are allocatedto the upper and lower pixel area commonly. At the lower side (or ‘upperside’), there is only one segment of the gate line GL is disposed.Considering one pixel area, in the first embodiment, the gate electrodesG1 and G2 are disposed at the upper side and the lower side. On thecontrary, in the second embodiment, the gate electrodes G1 and G2 aredisposed at only any one side of the upper and lower sides. Therefore,the second embodiment has merits in which the area ratio of the TFTs T1and T2 in the pixel area can be minimized. In some actual examples, thesecond embodiment has 15% 20% higher aperture ratio than the firstembodiment.

Further referring to FIG. 5, we will explain about the structure of thethin film transistor having the poly silicon semiconductor material inthe top gate structure according to the second embodiment of the presentdisclosure. On the substrate SUB, a semiconductor layer SE is formed. Onthe whole surface of the substrate SUB having the semiconductor layerSE, a gate insulating layer GI is deposited. On the gate insulatinglayer GI, a gate electrodes G1 and G2 overlapping with an active channellayers A1 and A2 (the middle portions of the semiconductor layer SE) isformed.

On the gate electrodes G1 and G2, an intermediate insulating layer IN isdeposited to cover the whole surface of the substrate SUB. Penetratingthe intermediate insulating layer IN and the gate insulating layer GI,formed are a source contact hole SH and a drain contact hole DH exposingthe source area SA1 of the driving TFT T1 and the drain area DA2,respectively. On the intermediate insulating layer IN, formed are asource electrode S1 of the driving TFT T1 contacting the source area SA1of the driving TFT T1, and a drain electrode D2 of the compensation TFTT2 contacting the drain area DA2 of the compensation TFT T2.

On the substrate SUB having the top gate type TFTs T1 and T2, a firstpassivation layer PAS1 is deposited. By penetrating the firstpassivation layer PAS1, a pixel contact hole PH exposing some portionsof the drain electrode D2 of the compensation TFT T2 is formed.

On the first passivation layer PAS1, a pixel electrode PXL contacts thedrain electrode D2 of the compensation TFT T2 via the pixel contact holePH. A second passivation layer PAS2 is deposited on the substrate SUBhaving the pixel electrode PXL. A common electrode COM is formed on thesecond passivation layer PAS2. The common electrode COM is overlappedwith the pixel electrode PXL by the second passivation layer PAS2therebetween. Between the pixel electrode PXL and the common electrodeCOM, the fringe electric field is formed. Further, the storagecapacitance is formed within the overlapped space between the pixelelectrode PXL and the common electrode COM.

Until now, we will explain about the thin film transistor substrate forthe liquid crystal display in which two thin film transistors having thepoly silicon semiconductor material are included in every pixel area.The concept of the present disclosure can be applied to other type thinfilm transistor substrate having other semiconductor material and otherTFT structure. Furthermore, even though these embodiments are focused onthe fringe field switching type liquid crystal display, the key conceptof the present disclosure can be applied to the in-plane switching typeliquid crystal display.

In the present disclosure, we will explain about the liquid crystaldisplay. The main idea of the present disclosure is to ensure highaperture ratio in the flat panel display having the super ultra highdensity resolution over 300PPI. Therefore, the main concept of thepresent disclosure can be applied to any flat panel display using thethin film transistor substrate such as an organic light emitting diodedisplay.

While the embodiment of the present invention has been described indetail with reference to the drawings, it will be understood by thoseskilled in the art that the invention can be implemented in otherspecific forms without changing the technical spirit or essentialfeatures of the invention. Therefore, it should be noted that theforgoing embodiments are merely illustrative in all aspects and are notto be construed as limiting the invention. The scope of the invention isdefined by the appended claims rather than the detailed description ofthe invention. All changes or modifications or their equivalents madewithin the meanings and scope of the claims should be construed asfalling within the scope of the invention.

What is claimed is:
 1. A thin film transistor substrate, comprising:gate lines running in horizontal direction and data lines running invertical direction which define a plurality of pixel area on asubstrate; a first gate electrode and a second gate electrode formed bydividing any one gate line disposed at any one of an upper side and alower side; a first thin film transistor connected to the first gateelectrode; and a second thin film transistor connected to the first thinfilm transistor and the second gate electrode.
 2. The thin filmtransistor substrate according to the claim 1, further comprising: asemiconductor layer extending from a first pixel area crossing the firstgate electrode to a second pixel area crossing the second gateelectrode, wherein a drain area of the first thin film transistor and asource area of the second thin film transistor are connected through thesemiconductor layer.
 3. The thin film transistor substrate according tothe claim 2, wherein the first thin film transistor includes: a firstsource electrode branching from the data line and contacting one side ofthe semiconductor layer; a first channel layer including a portion ofthe semiconductor layer overlapping with the first gate electrode; and afirst drain area extending from the first channel layer, wherein thesecond thin film transistor includes: a second source area extendingfrom the first drain area and including a portion of the semiconductorlayer; a second channel layer extending from the second source area andoverlapping with the second gate electrode; and a second drain electrodecontacting other side of the semiconductor layer extending from thesecond channel layer.
 4. The thin film transistor substrate according tothe claim 1, further comprising: a first semiconductor layer formed at afirst side and crossing the first gate electrode and the second gateelectrode to extend from the first pixel area to the second pixel area,wherein the first semiconductor layer is connected to a first pixelelectrode formed in the first pixel area, and the second semiconductorlayer is connected to a second pixel electrode formed in the secondpixel area.
 5. The thin film transistor substrate according to the claim4, wherein the first semiconductor layer is connected to the data linedisposed at one side, and the second semiconductor layer is connected tothe data line disposed at other side.
 6. The thin film transistorsubstrate according to the claim 1, further comprising: a pixelelectrode connected to the second thin film transistor; a passivationlayer covering the pixel electrode; and a common electrode overlappingwith the pixel electrode on the passivation layer.
 7. The thin filmtransistor substrate according to the claim 6, wherein the pixelelectrode is a surface electrode having a rectangular shape, and thecommon electrode is overlapped with the pixel electrode and has aplurality of segments which are disposed in parallel with certain gap.